MEETING OF THE HIP SOCIETY

Thirty-Fourth Open Scientific Meeting

The Twelfth Combined Open Meeting Hip Society and AAHKS

Chicago, IL

March 25, 2006

PROGRAM CHAIRMAN

William Capello, M.D.

CONTENTS:

Program

Abstracts

Hip Society Officers

AAHKS Officers

COURSE OBJECTIVES: The objectives of the Open Meeting of The Hip Society is to provide up-to-date information on the treatment of problems involving the young adult hip including avascular necrosis and the current thinking on bearing surfaces. Another objective is to provide a balanced view of MIS surgery and DVT prophylaxis. In addition, we will update our thinking on the treatment of femoral neck fractures including those in the pediatric age group.

COURSE DESCRIPTION: This course is divided into a series of symposia beginning with a look at the young adult hip and various treatment options as well as long-term data on the success rates of various modalities. This will be followed by a detailed look at bearing surfaces, highlighted by the presidential guest speaker. There will be other symposia giving a balanced look at DVT prophylaxis and MIS surgery. Other topics include new techniques in revision surgery as well as a look at periprosthetic bone loss. Finally, The Hip Society Awards Papers and a summarization of the proceedings of the Research Society as it applies to the adult hip will be included in the program.

 INTENDED AUDIENCE: The intended audience is orthopedic surgeons and orthopaedic residents.

Program:

7:55 a.m.

Opening Comments
James D’Antonio, M.D.


SYMPOSIUM I:  
YOUNG ADULT HIP
Moderator: Dennis Collis, M.D.
Eugene, OR


8:00 a.m.              
Osteotomy
Joel Matta, M.D.
Los Angeles, CA


8:07 a.m.              
Hip Joint Impingement
Robert Trousdale, M.D.
Rochester, MN


8:14 a.m.
Cemented Total Hips In Patients Less Than 50yrs
Graham Gie, M.D.
Exeter, UK


8:21 a.m.              
Outcome Of Uncemented Total Hip Arthroplasty
In Patients Aged 50 Years Or Younger
Cecil Roraback, M.D.
London, Ontario, Canada


8:28 a.m.
Hip Resurfacing for Patients under 50 years of age.
Results of 350 Conserve^® Plus With a 2-9 Year Follow-up
Harlan C. Amstutz, M.D.

Highly Crosslinked Polyethylene: Now and in the Future

John Flynn, M.D.
Philadelphia, P A


2:28 p.m.
Discussion


2:43p.m.
Break


SYMPOSIUM VIII:
REVISION SURGERY - ARE WE MAKING PROGRESS?
Moderator: Robert Bourne, M.D.
London, Ontario, Canada


3:03 p.m.
Fully Coated Stems - Is This The Gold Standard?
Daniel Berry, M.D.
Rochester, MN


3:10p.m.
Femoral Revision Arthroplasty With Fluted Modular Titanium Stems
Donald Garbuz, M.D.
Vancouver, British Columbia, Canada


3:17p.m.
Cages - The Current Role
Wayne Paprosky, M.D.
Winfield, IL


3:24 p.m.
Trabecular Metal In Acetabular Reconstruction
David Lewallen, M.D.
Rochester, MN


3:31 p.m.
Impaction Grafting Of The Socket
John Timperley, Ph.D.
Exeter, UK


3:38p.m.
Discussion


SYMPOSIUM IX:
MIS (MINIMALLY INVASIVE SURGERY)
Moderator: Arlen D. Hanssen, M.D.
Rochester, MN


3:53 p.m.
Patient Selection Variables for Minimally Invasive Surgery
Thomas Sculco, M.D.
New York, NY


SURGICAL APPROACHES:


4:00 p.m.
Direct Anterior Approach
William Hozak, M.D.
Philadelphia, P A


4:07 p.m.
The 2-Incision THA: Its Role in 2006
Mark Pagnano, M.D.
Rochester, MN


4:14 p.m.
Management of Peri-Operative Pain
Lawrence D. Dorr, M.D.
Inglewood, CA


4:21 p.m.
Comprehensive Approach To Rehabilitation
Benjamin Bierbaum, M.D.
Boston, MA


4:28 p.m.
Measurable And Clinically Relevant Outcomes
Aaron Rosenberg, M.D.
Chicago, IL


4:35 p.m.
Discussion


5:00 p.m.

Adjourn

Abstracts:

8:00 a.m.

Young Adult Hip: Osteotomy

Joel M. Matta, M.D.

For young adult hips, the primary causes of arthritis are acetabular dysplasia and femoral-acetabular impingement. Periacetabular Osteotomy has evolved over the past 20 years as the preferred treatment for acetabular dysplasia and is now supported by a number of follow-up studies.

Periacetabular Osteotomy was first performed in Bern Switzerland in 1984. Its impetus came from Reinhold Ganz, Chief of Orthopedics at the Inselspital, Bern and Jeffrey Mast. This osteotomy is a rotational acetabular osteotomy for correction of acetabular dysplasia. Like the preceding dial osteotomy it allows an essentially unlimited rotational correction and does not transect the posterior border of the innominate bone. As an advantage over the dial osteotomy, the periacetabular osteotomy allows a change in the center of rotation. The dysplastic hip typically has a center of rotation that is in a proximal and lateral position leading to an abnormal Shenton's line. This osteotomy tends to restore Shenton's line by bringing the center of rotation into a more medial and distal position. An advantage of the Periacetabular over the Dial besides the center of rotation change is that it is performed from the inside of the pelvis without disruption of the gluteal muscles on the external aspect of the bone. Other traditional pelvic rotational osteotomies such as the Steele, Sutherland, and Salter, do not have the same potential for rotational correction, may lead to pelvic deformity, and often retrovert the acetabulum.

Periacetabular osteotomy is indicated for patients with symptomatic acetabular dysplasia and following triradiate cartilage closure. The age range in this group is 15 to 55. The ideal indication is acetabular dysplasia patients with pain, good range of motion, a normal joint space, minimal arthritic changes, a spherical femoral head, and good congruence and coverage on the abduction internal rotation view. The majority of candidates are female and usually have a more predictably positive result than males. Older patients should meet ideal criteria where as younger patients are candidates despite less than ideal criteria. Proximal femoral osteotomy is simultaneously performed in a minority of patients to correct femoral deformity and/or enhance congruence and coverage.

From 1987 to 2005 the author performed 251 periacetabular osteotomies in 233 patients (18 bilateral). 19 associated femoral osteotomies were performed. The average patient age was 32 years old. Across the entire series, the median operative time was 2.5 hours and the median blood loss was 700 cc. The operative time and blood loss were compared between the first 50 surgeries and the last 50 surgeries in the series; median operative time was 3 hours in the first 50 surgeries and 1.5 hours in the last 50 surgeries. Median blood loss was 1000cc in the first 50 surgeries, and 375 cc in the last 50 surgeries. 142 patients were available with a minimum of 1-year follow-up; with an average follow-up of 4.14 years (range 1-15 years). At their most recent follow-up, 19% of patients had an excellent clinical result; 60% had a good clinical result, 14% had a fair clinical result, and 7% had a poor result. Six patients underwent subsequent total hip replacement.

8:07 a.m.

Hip Joint Impingement

Robert T. Trousdale, M.D.

The majority of patients who develop hip arthritis have a mechanical abnormality of the joint. The structural abnormalities range from instability (DDH) to impingement. Impingement leads to osteoarthritis by chronic damage to the acetabular labrum and adjacent cartilage.

In situations of endstage secondary DJD, hip arthroplasty is the most reliable treatment choice. In young patients with viable articular cartilage, joint salvage is indicated. Treatment should be directed at resolving the structural abnormalities that create the impingement.

Femoral abnormalities corrected by osteotomy or ( head-neck offset by chondro-osteoplasty creating a satisfactory head-neck offset. This can safely be done via anterior surgical dislocation. The acetabular-labral lesions can be debridement and/or repaired. Acetabular abnormalities should be corrected by "reverse" PAO in those with acetabular retroversion or anterior acetabular debridement in those with satisfactory posterior coverage and a damaged anterior rim.

Often combinations of the above are indicated.

8:14 a.m.

Cemented Total Hips In Patients Less Than 50yrs

S Lewthwaite, B Squires, G. Gie, AJ Timperley, J Howell, M Hubble, Prof. R Ling.

The Cemented Exeter Total Hip Replacement was introduced into clinical practice in 1970 and since that time has been used in Exeter in patients of all ages. Although cementless sockets with ceramic bearings are now used in young patients, the cemented stem remains our treatment of choice for all age groups.

In 1988 modularity was introduced into the system and since that time the Exeter Hip Research Unit has prospectively gathered data on all patients who have had total hip replacements (THR's) at the Princess Elizabeth Orthopaedic Hospital. A recent review has been conducted to determine the medium- to long-term term survivorship and function of the Exeter Universal Hip Replacement when used in younger patients, a group that is deemed to place high demands on their arthroplasties

There were 130 Exeter Hips in 107 patients who were 50 years or younger at the time of surgery and whose surgery had been performed a minimum of 10 years previously . Mean age at surgery was 42y (range 17y to 50y). 6 patients who had 7 THR's had died, leaving 123 THR's for review. Patients were reviewed at an average of 12.5 years (10 - 17 years) post-op. No patient was lost to follow up.

Results: At review, 12 hips had been revised. Of these, 9 were for aseptic loosening of the acetabular component and one cup was revised for focal lysis and pain. One hip was revised for recurrent dislocation. One femoral component required revision in 1 case of infection. Radiographs showed that a further 11 (10%) of the remaining acetabular prostheses were loose but that no femoral components were loose. Survivorship of stem and cup from all causes was 94% into the seventeenth year. With any reason for revision of the stem as the end-point, survivorship was 99% and with aseptic loosening as the end-point, survivorship was 100%.

Conclusion: The Exeter Universal Stem is shown to perform extremely well in the younger patient. No femoral component became loose and only 7.3% of acetabular components were revised for aseptic loosening at a follow-up period of 10 to 17 years.

8:21 a.m.

Outcome Of Uncemented Total Hip Arthroplasty

In Patients Aged 50 Years Or Younger

Cecil H. Rorabeck, M.D., F.R.C.S.C., SR Kearns M.D., F.R.C.S.I. (Tr & Orth), J. Bilal

Providing a long-lasting total hip arthroplasty (THA) for the young patient with hip arthritis remains one of greatest challenges for modern arthroplasty surgery. Between 1983 and 2000, 221 patients underwent 298 uncemented THAs at our institution. 10, 15 and 20-year survival was assessed, with any aseptic revision as the end-point. Latest radiographs were assessed for polyethylene wear, component loosening and osteolysis. Femoral stem survival was 98.9(97.7-100%)%, 96.8(92.5-100%)% and 90.7(78.5-100%)% at 10, 15 and 20 years. Acetabular component survival was 84.6(78.8-90.4%)%, 52.5(40.7-64.3%)% and 23.3(6.8-39.8%)% at 10, 15 and 20 years. Excluding polyethylene liner exchange, this increased to 90.6(85.7-95.5%)%, 65.3(52.8-77.8%)% and 55.4(38.8-72%)% at 10, 15 and 20 years. THAs performed for hip dysplasia and avascular necrosis had lower 10-year survival. 69 revisions were performed, the commonest indication being polyethylene wear (n=33). In unrevised THAs 40.3% showed asymmetric polyethylene wear. Zirconium on polyethylene articulations had significantly lower acetabular revision rates compared with cobalt-chrome on polyethylene (p=0.02). Uncemented femoral stems provided over 90% survivorship at a minimum 20-year follow-up. Contemporary bearing surfaces in association with such stems may provide long lasting THAs even in young active patients.

8:28 a.m.

Hip Resurfacing for Patients under 50 years of age.

Results of 350 Conserve^® Plus With a 2-9 Year Follow-up

Harlan C. Amstutz, M.D., Scott T. Ball, M.D.,

Michel J. Le Duff, M.A. and Frederick J. Dorey, Ph.D

Introduction:  Patients under 50 years of age with degenerative diseases of the hip pose a difficult treatment challenge.  Historically, total hip replacement in this high demand patient population has demonstrated diminished survivorship. Because it saves the femoral head and is easily revisable resurfacing arthroplasty of the hip is an attractive treatment option for young, active patients. The purpose of the present study was to determine the effectiveness of metal-on-metal hip resurfacing for the treatment of patients under 50 years of age.

Materials and Methods: From a consecutive series of over 900 Conserve^® Plus metal-on metal hybrid resurfacings, 350 hips  were resurfaced in 295 patients less than 50 years old. The average age of the patients was 41.2 years (range, 14 to 49) 75% were male. ”Idiopathic” OA was the etiology in 50%, DDH in 16%, trauma in 11%, ON in 11%, LCP and SCFE 7%, Inflammatory diseases 4%, and others (PVNS and melorheostosis) less than 1%.  All femoral components were cemented with an approximate 1mm cement mantle.  The femoral metaphyseal stem was cemented in 105 hips and press-fit in the remaining 245.  All acetabular components were pressfit.

Results:  Average follow-up was 5.3 years (range, 1.6 to 9.1).  UCLA hip scores improved significantly from before surgery to most recent follow-up (pain: 3.4 to 9.4; walking: 6.0 to 9.6; function: 5.6 to 9.5; activity: 4.5 to 7.6.)  There have been no cases of acetabular component loosening. There has been a 2.8% rate of revision for femoral aseptic loosening (10 hips) and one femoral neck fracture.  An additional eight hips (2.3%) have radiolucencies about the femoral stem. All are asymptomatic but one who was lost to follow-up. Lastly, there has also been one revision for late hematogenous sepsis and 1 for recurrent subluxation from impingement. Of these failures, the average surface arthroplasty risk index (SARI) was significantly higher than the average of the entire cohort (4.3 compared to 2.6, p=0.0001). There has been no femoral component loosening when the femoral stems were cemented in.

Conclusions:  Metal-on-metal resurfacing arthroplasty of the hip is performing well at short to mid-term follow-up in young, active adults despite their high activity levels. Cementing the stem of the femoral component appears to be important, particularly in patients with risk factors. Patient selection and surgical technique are essential in improving outcomes in hips with risk factors.

8:35 a.m.

Osteonecrosis: A New Era

David S. Hungerford, M.D.

Osteonecrosis (ON) of the femoral head has been a significant orthopedic problem for the last 100 years. At first it was a problem of diagnosis and separation from severe OA of the hip. Since it has been separated diagnostically, it has been a therapeutic problem. The significant improvement in outcome that came to suffers of OA of the hip in the 1970's turned out to be fools gold for most patients with osteonecrosis. Although high failure rates were experienced in most categories of THR in young active patients, THR in ON patients turned out to be particularly problematic. Conservative (non-operative) management appeared to offer virtually no hope, and preservative therapy, didn't work for most patients, and often involved surgery associated with marginal success rates and exposure to significant morbidity and complications. That was the unhappy truth for ON. This lead to a nihilistic approach, of widespread advice to patients to 'hold on for as long as you can and when you can't stand it any more we will do a total hip replacement'.

It appears to me that the new bearing surfaces offer a much brighter future for patients with ON. The majority of patients present with advanced large lesions. In the past, surgeons could be justified in doing large complex operations with success rates in the 70% range because of the miserable success rate of THR and the specter of multiple revisions with increasing complication rates and dwindling success. With the new bearing surfaces and the high success of current cementless offerings, this posture can no longer be justified. Proximal femoral osteotomies, and free vascularized bone grafts are procedures that are associatd with significant morbidity and alter the proximal femur, complicating subsequent THR. These and limited femoral head resurfacing were often justified to 'buy time' until THR technology could catch up with patient need. That time has now come!

There still are some cases that present with moderate sized lesions that have not yet collapsed. Core decompression and bone grafting can still be justified because of the limited nature of the procedure, the low complication rate and the lack of consequence on subsequent THR. With some of the newer bone graft substitutes and bone stimulating biologics, the success rate of these procedures may be further enhanced. However with three long lasting highly durable bearing surfaces to choose from; metal-metal, ceramic-ceramic and metal on highly crosslinked Polyethylene, fear of Total hip replacement is not the driving factor that it was as recently as five years ago.

9:00 a.m.

Wear of Hip Prostheses:

Influence of Material and Head Size

John Fisher, M.D.

Younger and more active patients are now demanding reduced wear and increased osteolysis free lifetimes, as well improved function, range of motion and stability, in the choice of their hip prostheses With more active patients undertaking up to five million steps per year and life expectancies in excess of 30 years, this can deliver in excess of a ten fold increase in the functional tribological demand of the wear life of the bearing, in comparison to a lower demand elderly patient. The more active patients also demand improved biomechanical functional associated with larger head sizes. However this can lead to an intrinsic design contradiction with polyethylene acetabular cups, where larger head sizes can lead to increased sliding distances and increased wear rates. In conventional polyethylene acetabular cups, wear rates of 30 mm3/million cycles with size 28mm femoral heads, may provide up to twenty years osteolysis free lifetimes for low activity patients, but the osteolysis free lifetime is markedly reduced if patient activity or head size is increased. Alternative material combinations now have to be considered for these high demand patients.
Highly cross linked polyethylene has shown a four fold reduction in wear rates compared to conventional polyethylene, but the wear particles have been shown to be smaller and twice as reactive, resulting in only a two fold reduction in functional osteolytic potential. Consideration has to be given as to whether this improvement in the biomaterial wear performance is sufficient to recommend use with large diameter heads or with patients with up to a ten fold increase in functional tribological demand.

Alumina ceramic on ceramic bearings, have between a twenty five to 1000 fold reduction in wear volume compared to polyethylene bearings and the wear particles show a two fold reduction in biological activity. So even with the highest wear rates found under conditions of microseperation, the ceramic on ceramic bearings show a fifty fold reduction in functional osteolytic potential, and allow larger size 36mm diameter heads to be used, providing improved biomechanical function as well as extended wear life.

Metal on metal bearings have a twenty five to 500 fold reduction in wear rate compared to conventional polyethylene bearings. Wear rates are critically dependent on design and radial clearance with lower radial clearance giving lower wear). For these lubrication sensitive bearings, wear is predicted to reduce with larger head sizes. There are concerns that the nanometre size metal wear particles can cause hypersensitivity and elevated ion levels, and there is considerable interest in use of larger diameter bearings such as surface replacements that have even lower wear rates.
Recent experimental studies have shown a further reduction to metal on metal wear with novel differential hardness ceramic on metal bearings and with surface modified metal on metal bearings. Future clinical studies will reveal whether these will also lead to reduced metal ion levels in vivo.
As the functional and tribological demands of patients increase, alternative hard on hard bearings are required to provide low wear and extended osteolysis free life times, when coupled with larger head diameters.

9:20 a.m.

US Experience with Alumina Ceramic-Ceramic THA

Stephen Murphy, Timo Ecker, Moritz Tannast, Benjamin Bierbaum,

Jonathan Garino, Eric Hume, Richard Jones, Robert Zann, Kristaps Keggi and Kenneth Kress

Bearing wear and associated osteolysis are the most common problems affecting the long-term results of total hip arthroplasty. Alumina ceramic-ceramic bearings have been introduced as one method of addressing these problems. The current study reviews the clinical outcome of the use of alumina ceramic-ceramic bearings in the United States and specifically reports on the 2 to 8 year results of 22 surgeons who participated in an FDA-IDE study.

1687 THA were performed in 1466 patients using alumina ceramic-ceramic bearings (Transcend(r) and Lineage(r) acetabular components, Wright Medical Technology, Inc.) by 22 surgeons in the US from April, 1997 to February, 2003 and studied prospectively. Of these, 1031 hips were followed for a minimum of 24 months (range 24 to 101 months), mean 47.91 months. Patients were aged 52.08 +/- 10.77 years (range 18-81 years).

Results. Of the 1687 THA's, aseptic revisions included femoral component revision for loosening or failure of osseointegration in 11 hips and of the acetabular component in 2. Three hips were revised for acetabular liner fracture and one was revised for femoral head fracture. Other revisions included three hips with mis-matched head-liner bearing diameters and one hip where the liner was not properly seated. Two hips were converted to a non-ceramic bearing during the index operation for use of a lipped-liner or extended head. One hip was revised for recurrent instability. 7 hips were revised for infection. 3 hips were revised in association with periprosthetic fracture. There have been no other cases of wear and no cases with osteolysis in any unrevised hip as visible on plain radiographs. 8 year Kaplan-Meier Survivorship for revision of any component for loosening or bearing failure is 97.3 % (Standard Error 0.008).

Results of data from this prospective FDA/IDE demonstrate that the alumina ceramic-ceramic bearings are reliable and show very few early problems. Ceramic fractures do occur rarely and may be similar in incidence to reports of fractures of polyethylene components. The incidence of instability is extremely low despite the absence of lipped liners and fewer head-length options. The bearings continue to demonstrate the absence of osteolysis in this series of more than 8 years maximum follow-up.

9:27 a.m.

Metal-On-Metal Bearings: State-Of-The-Art And Science In 2006

Joshua J. Jacobs, M.D., Nadim Hallab, PhD, Robert Urban,

Anastasia Skipor, M.S. and Marcus Wimmer, PhD.

There continues to be keen interest in the application of metal-on-metal bearings in total hip and hip resurfacing arthroplasty. The advantages of metal-on-metal bearings include a substantially lower volumetric wear rate in comparison to conventional metal-on-polyethylene bearings, easy fabricability, high fracture toughness, and the ability to use large femoral heads thereby improving the range of motion and lessening the risk of postoperative instability. The major disadvantage of metal-on-metal bearings relates to the potential intermediate- and long-term biological effects of chronic elevations in local and systemic cobalt and chromium levels. Even though volumetric wear rates are substantially reduced compared to conventional bearing couples, metal-on-metal bearings actually produce a greater number of particles since the debris generated is in the nanometer size range, likely as a consequence of wear-induced metallurgical transformations (recrystallization and martensite formation) at or near the surface. While the bioreactivity of nanometer-sized cobalt-alloy debris is not well-characterized, large numbers of such minute particles yields a relatively high specific surface area (surface area/mass) available for dissolution (corrosion) of these particles. This may account, at least in part, for the substantial elevations in serum and urine cobalt and chromium concentration that have been documented by numerous investigators.

As more experience is gained with the so-called second-generation metal-on-metal bearings, intermediate-term clinical results are now becoming available. While these studies are generally favorable, there have been reports of early osteolysis, possibly related to metal hypersensitivity. In addition, histopathological studies on tissues retrieved from patients with failed metal-on-metal devices reveal a pattern of lymphocytic response that is distinct and suggestive of a delayed-type hypersensitivity response.

In the high demand patient, metal-on-metal bearings remain a viable option for total hip arthroplasty and the only currently available option for surface arthroplasty. Continued surveillance of populations with metal-on-metal devices is warranted to determine whether there is a demonstrable long-term survivorship advantage associated with the use of these bearings and to determine whether chronic elevations in systemic metal content are tolerated in the long term.

9:34 a.m.

Highly Crosslinked Polyethylene:

Now and in the Future

William J. Maloney, M.D.

Highly crosslinked polyethylene was introduced more than five years ago to address the most common long term complication in total hip replacement, osteolysis associated with the biologic reaction to polyethylene wear debris. The hypothesis was that enhanced crosslinking would decrease the wear volume and thus decrease the incidence of osteolysis. Prospective clinical trials have been performed evaluating many of the currently available products. In general the results have been excellent demonstrating a significant reduction in wear even at two years. Follow-up is too short to conclude that there will be a corresponding reduction in osteolysis.

Two potential problems have been identified with the first generation products. The first relates to in vivo oxidation. One product is manufactured is such a way so that the implant has a relatively high oxidation potential. Early retrievals have shown oxidation and the formation of a white band primarily in the non-weightbearing regions of the component. However, to date, this has not correlated with accelerated wear in prospective studies. The second problem relates to decreased mechanical properties of highly crosslinked polyethylenes compared to conventional material. Polyethylene fracture has been reported in a limited number of cases. Factors unique to these cases include the use of large femoral heads and elevated rim liners with malpositioned sockets. The net effect is loading of unsupported polyethylene and subsequent fracture. Both issues are currently being addressed with the next generation of crosslinked polyethylenes which are currently undergoing laboratory and early clinical evaluation.

9:41 a.m.

The Future of Hip Bearings

Michael T. Manley, Ph.D.

Contemporary bearing technologies continue to decrease wear debris in the hip and reduce the potential for osteolysis in young patients in the medium term. However, an overlooked consequence of present acetabular designs is the abnormal stress distribution in acetabular bony structures caused by stiff, well-fixed acetabular shells. Stress analysis of the normal acetabulum and the acetabulum with hemispherical shells of different material properties demonstrates the adverse remodeling potential associated with all contemporary designs in the young pelvis. Concomitant reduction in bone density may make acetabular structures less resistant to wear debris intrusion.

Comparison of hemispherical acetabular shells with more geometrically flexible designs shows an improvement in acetabular stress state with the geometrically flexible devices. It is likely that the future of acetabular bearings and acetabular reconstruction is a hard head/flexible socket bearing couple that can address current concerns, such as wear and bearing noise, while at the same time prevent long-term stress related deterioration of bony structures.

10:25 a.m.

Periprosthetic Bone Loss: Introduction of the Problem

John J. Callaghan, M.D.

In 1968 Charnley reported a pattern of non-linear endosteal erosion of bone in association with cemented total hip arthroplasty. Since that time, numerous authors have demonstrated the phenomenon of "osteolysis" around both cemented and cementless femoral and acetabular components. Over the years, surgeons and basic science investigators have come to understand the importance of nanometer size wear generated particles in the development of "osteolysis" type periprosthetic bone loss. In addition, the understanding of the contribution of access channels for wear particle transport has been recognized. More recent work has centered around the contribution of fluid pressures generated in the total hip arthroplasty construct.

In addition to the "osteolytic" pattern of bone loss, bone loss associated with "stress shielding" around implants has been described and investigated. The phenomenon has been reported around both cemented and cementless implants. The contribution of the initial bone quality at the time of hip replacement has been suggested as a major factor in the extent of bone loss related to stress shielding. Investigators have demonstrated the difficulty in differentiating bone loss related to stress shielding versus that related to wear particle generation, and the potential additive effect of these two phenomenon. A better understanding of the factors contributing to bone loss should enable surgeons and implant designers provide total hip arthroplasty constructs for our patients which limit the bone loss associated with the long term function of these constructs.

10:32 a.m.

Nonsurgical Management of Osteolysis: Challenges and Opportunities

Harry E. Rubash, M.D., Carl Talmo, M.D. and Arun Shanbhag, Ph.D., M.B.A.

Recent technological advances in bearing surfaces have resulted in significant reductions in wear and potential improvements in implant longevity, however, osteolysis currently remains a major source of failure in total hip arthroplasty In vitro and animal models have been instrumental in determining the pathophysiology of this disease and also carefully dissecting the biochemical pathways by which particulate wear debris leads to peri-implant bone loss. Numerous cytokines and inflammatory mediators, including TNF-?, and IL-1 are critical participants in this cascade and may represent prime targets for pharmacologic intervention. Osteoclasts, the end effector cells involved in the osteolytic process, also represent potential targets. Cell surface receptors on osteoclast precursors such as RANK on osteoclasts and RANK-ligand on stromal cells provide opportunities to arrest osteoclast maturation. Enhancing the naturally occurring osteoprotegrin represents another recent attempt at modulating osteoclast behavior and a possible target for pharmacologic therapies.

In this presentation, we will succinctly summarize the various strategies attempted by investigators: from intercepting TNF-? activity, interfering with the RANK-RANKL interaction necessary for osteoclast development and maturation, bisphosphonate therapy, to using viral vectors to deliver genes. The challenges of each of these approaches as well as their opportunities will be summarized. Until there is convincing evidence of efficacy in human clinical trials, the recommended management of osteolysis around THA remains vigilant screening and appropriate surgical intervention when there is the presence or potential for component loosening, periprosthetic fracture or major bone loss.

10:39 a.m.

Acetabular Bone Loss

Charles A. Engh, Sr., M.D.

Bone loss following total hip arthroplasty falls into two categories, bone loss that occurs due to stress-induced bone remodeling and bone loss from osteolysis. Although both types of bone loss can begin immediately after implantation, stress induced bone loss, or stress shielding, can be detected on radiographs approximately 1 to 2 years postoperatively while bone loss caused by osteolysis can be detected at 6 or more years postoperatively.

Bone loss by both etiologies is easier to visualize and quantify in the femur than in the pelvis for two reasons. First, the simpler cylindrical geometry of the femur and the ability to rotate a patient's leg make it possible to view the stem inside the femur at multiple projection angles. The complex geometry of the pelvis also makes it difficult to obtain more than a few reproducible x-ray projections. Second, the bone loss that occurs in the femur is predominately cortical rather than cancellous, which is easier to detect on radiographs and DEXA. Plain radiographs and DEXA are less effective for identifying and quantifying bone loss behind an acetabular shell since the bone loss is predominately cancellous.

We have found the most reliable method to assess pelvic bone loss to be quantitative CT of hemipelves obtained from patients at autopsy. The ideal patient is one who has had a unilateral hip total hip arthroplasty. Both the implanted and non-implanted hemipelves, devoid of soft tissue and the femoral component, can be scanned by CT in identical orientation. Using high kV settings that are not safe for living patients, any beam scatter from the thin titanium shell can be eliminated. The resulting images from each side can then be compared for changes in cancellous bone density behind the acetabular shell.

The pattern of bone loss of a hip implanted with an acetabular shell is dependent on whether the porous coating on the shell has become osseointegrated, meaning that it has become fixed by bone growth inside the sintered beaded or fibermesh surface. When bone ingrowth has occurred, a characteristic pattern of bone remodeling can be clearly identified on the CT images. Any residual subchondral plate is resorbed and replaced by the more rigid titanium shell. If the shell was positioned at surgery to have maximum cortical contact with the acetabular rim, and the acetabular fossa remains intact, cancellous bone atrophy occurs behind the dome of the shell and cortical hypertrophy occurs at the rim at the areas of localized cortical contact. These changes are usually not visible on serial plain radiographs because radiographs are so sensitive to slight alterations in technique. Additionally, since DEXA predominantly records cortical bone loss, and this stress-induced bone remodeling consists mostly of cortical bone atrophy, the changes are difficult to detect by DEXA.

Despite having over 25 years of experience, the authors have not been able to document either a cup loosening or stem loosening resulting from stress induced bone remodeling. In fact, if these changes are not visible in the femur, the authors believe that the femoral component is probably not osseointegrated and that late failure is more likely to occur than if the changes are present.

Pelvic osteolysis represents a very different pathologic process than stress shielding. Soft unstressed bone near the joint is resorbed when it comes in contact with joint fluid under increased pressure, particularly if the joint fluid contains particulate debris. The radiographic definition of osteolysis is quite different than that of stress shielding and includes 1) a localized expansile area devoid of cancellous bone, 2) a sclerotic border, and 3) a clear communication pathway between the lytic area and the joint space. CT is much more accurate for diagnosing pelvic osteolysis than plain radiographs and with modern CT technology, the 3 distinguishing radiographic features are always visible. CT is particularly valuable for detecting small lesions hidden on plain radiographs behind the cup and for confirming the connection to the joint space, which often can not be defined on radiographs. Finally, CT also is advantageous since it allows for accurate measurement of lesion volume.

In contrast to stress-induced bone remodeling, which seems to stabilize after a few years, pelvic osteolytic lesions almost always progressively enlarge in a linear manner. Although the authors have visualized many extremely large lesions in the pelvis at late follow-up, very few resulting complications, such as cup loosening or pelvic fracture, have been observed. As a result, the best method of surgical treatment of this condition is unknown.

10:46 a.m.

New Femoral Designs --- Do They Influence Stress Shielding?

Andrew H. Glassman, M.D., M.S. and J. Dennis Bobyn Ph.D.

Stress mediated bone resorption -"stress shielding"- is influenced by host factors (e.g. pre-operative bone mineral density), implant factors (stem stiffness, extent of ingrowth surface), and by the rigidity of implant fixation to host bone. The role of femoral component design has been long recognized and is the focus of this presentation.

Stem stiffness is the product of stem geometry and modulus of elasticity of the alloy or composite from which the implant is fabricated. Implant stiffness can therefore be manipulated by changes in materials, stem shape, or both. Early attempts at reducing stem stiffness focused upon stem materials, employing various polymer-metal composites. Many such designs suffered mechanical failure attributable to poor fatigue strength of the surface polymers. Titanium alloy was recognized as suitably strong with a lower modulus than cobalt chromium alloys. Within certain size ranges, the use of titanium versus cobalt alloy stems results in reduced stress shielding.

A subsequent strategy was the limitation of the ingrowth surface to the proximal implant. It has been clearly demonstrated that in so doing, for similarly shaped implants of identical composition, the distal extent of stress shielding is significantly reduced. However, in concentrating the area of load sharing to the most proximal femur, the severity of bone loss per unit of bone is actually increased.

Recent attempts to reduce implant stiffness have centered largely upon changes in stem geometry; specifically, the removal of implant material to reduce the cross-sectional moment-area and hence, the bending stiffness of the stem. Medial "cut-outs", "clothespin" designs, and flutes are examples of efforts to reduce the mid- and distal stem stiffness. However, the geometric contribution to stem stiffness is most pronounced in the bulkier proximal aspect of the stem. There is a paucity of data in the form of controlled studies using DEXA analysis to demonstrate that such design changes reduce stress shielding. Previously, some advocated maximum proximal "fit-and-fill" with bulky metaphyseal-filling implants. Such designs, despite being proximally coated, were associated with significant stress shielding. Wedge-shaped stems that are flatter in the anterior-posterior dimension demonstrate less stress shielding than canal-filling stems that fill the femur more completely.

Clinical trials with a contemporary composite stem began in the United States and abroad in 1994. The stem features a solid cobalt chromium core covered with a polymeric layer enclosed by an extensive porous coating of titanium fiber metal. DEXA studies demonstrate a significant reduction in stress shielding as compared to similarly sized and shaped implants fabricated of solid metal.

Clinically, stress shielding is usually associated with bone ingrowth and a favorable clinical result. To date, no data suggests a correlation between stress shielding and a risk of adverse events such as femoral shaft or trochanteric fracture, or osteolysis. However, in the event that a well-fixed stem requires removal for late infection or other cause, significant stress shielding complicates removal and compromises the bone stock remaining for reconstruction.

11:15 a.m.

Who is at risk?

Eduardo A. Salvati M.D., Burak Beksac M.D.

and Alejandro Gonzalez Della Valle, M.D.

The activation of the clotting cascade that occurs during total hip arthroplasty (THA) places patients at risk for venous thromboembolism (VTE). A thorough review of the current literature recognizes the following predisposing factors, outlined in order of importance: hip fracture, malignancy, particularly if associated with chemotherapy, antiphospholipid syndrome, history of VTE, immobility, administration of tamoxifen, raloxifene, oral contraceptives or estrogen; morbid obesity, stroke, atherosclerosis and American Society of Anesthesiologists (ASA) Physical Status Classification of 3 or greater. The following risk factors are considered weak or controversial: advanced age, diabetes mellitus, certain cardiovascular conditions, such as congestive heart disease and atrial fibrillation, varicose veins, and smoking.^{1, 2}

However, 50 % of patients who develop thromboembolism after THA have no clinical predisposing factors. ³ Since the late 1990s, there has been an increased awareness of the role of heritable thrombophilia and hypofibrinolysis in the development of VTE. Combinations of these genetic factors with one another or with the recognized clinical risk factors previously mentioned multiply rather than add to the risk of VTE.⁴

We have defined in a matched controlled study the major genetic predispositions which increase the risk of VTE after THA: deficiency of antithrombin III (<75%) and of protein C (<70%), and homo-heterozygosity for the prothrombin gene mutation.⁵ Pre-operative genetic screening for these factors, in conjunction with the recognized clinical risk factors previously mentioned, can identify postoperative VTE risk and differentiate patients who could be protected with milder and safer forms of prophylaxis (aspirin, intermittent pneumatic compression), with those at higher risk who need to be anticoagulated. Preoperative genetic screening is cost effective. ⁵

1.        Heit JA, O'Fallon WM, Petterson TM, Lohse CM, Silverstein MD, Mohr DN, Melton III LJ: Relative Impact of Risk Factors for Deep Vein Thrombosis and Pulmonary Embolism: A Population-Based Study. Arch Intern Med 162:1245-1248, 2002.

2.        Salvati EA, Pellegrini VD, Jr., Sharrock NE, Lotke PA, Murray DW, Potter H, Westrich GH: Recent advances in venous thromboembolic prophylaxis during and after total hip replacement. J Bone Joint Surg Am 82:252-270, 2000.

3.        Gonzalez Della Valle A, Serota A, Go G, Sorriaux G. Sculco T, Sharrock N, Salvati E: Venous thromboembolism is rare after THR with a multimodal prophylaxis protocol. In press, Clin.Orthop 444, March 2006.

4.        Lane DA, Grant PJ: Role of haemostatic gene polymorphisms in venous and arterial thrombotic disease. Blood 95:1517-1532, 2000.

5.        Salvati EA, González Della Valle A, Westrich GH, Rana AJ, Specht L, Weksler BB, Wang P, Glueck CJ. Heritable thrombophilia and development of thromboembolic disease after total hip arthroplasty. THE CHARNLEY HIP SOCIETY AWARD. Clin.Orthop 441:40-55, 2005.

11:22 a.m.

Low Molecular Weight Heparin for DVT Prophylaxis

Clifford W. Colwell Jr., M.D.

Low molecular weight heparins (LMWH) have been studied extensively in total hip arthroplasty (THA) and provide both highly effective and safe DVT prophylaxis. Low molecular weight heparin received the highest rating, A1, in the American College of Chest Physicians (ACCP) recommendations for use in DVT prophylaxis after elective total hip arthroplasty. The prevalence of DVT with LMWH prophylaxis was 16% in a combination of THA studies involving over 6,000 patients, with a relative rate reduction of 70% compared to placebo. In these same studies, the prevalence of proximal DVT was 6%. LMWH is given by subcutaneous injection and can be started 12 hours before surgery, or 12 to 24 hours after surgery, or 4 to 6 hours after surgery at half the usual dose. Major bleeding rate reported for low molecular weight heparin is about 5% compared with about 4% in placebo trials. According to the GLORY data, surgeons in the USA report using LMWH prophylaxis on 43% of THA cases compared with a reported 90% in other countries. Also available is a synthetic pentasaccharide, fondaparinux, which also received an A1 rating in the ACCP recommendations. Combining two studies with over 1,600 patients, the overall DVT rate was 5% with a proximal DVT rate of approximately 2%. No major bleeding was reported, but overall bleeding was 3%. As with all interventions, the benefit has to be considered against the risk in use of these anticoagulants.

11:29 a.m.

The Use of Aspirin for Prophylaxis Against

Thromboembolic Disease After Total Joint Surgery

Paul A. Lotke M.D.

Introduction: The threat from thromboembolic disease has been dramatically reduced during the past decade. Currently the risk for fatal PE after total joint surgery approximates 0.1%. The risk is consistent and does not appear to vary with different prophylactic regimens. This reduction in risk may be due to a confluence of medical advances that have occurred in the past decade including: widespread utilization of regional anesthesia; improved surgical techniques; rapid mobilization after surgery; newer analgesia regimens which assist in rapid mobilization; and the general awareness of compression devices and the available chemotherapeutic agents. In order to decide which regimen is best for our patients, each surgeon must carefully weigh the risks and benefits of their choice.

Aspirin is an effective anti-platelet agent and has been used for decades by orthopaedic surgeons for prophylaxis against thrombolembolic disease. It permanently inactivates the cyclooxygenase activity of prostaglandin H (cox 1) with dosage as low as 30-50 mg/day. Since the newer anticoagulants, like the low molecular weight heparins, reduce the incidence of DVT more efficiently, aspirin is perceived by some not to be as effective. However, its safety, clinical effectiveness and ease of extended dosing, make it very attractive and it continues to be used by many orthopaedic surgeons. This discussion reviews our experience with aspirin as the main chemoprophylactic agent after total knee surgery.

Methods: We have followed every one of 2817 consecutive total knee patients for a minimum of 6 weeks. Aspirin, 325 mg twice a day for six weeks, was the principle chemoprophylactic agent in all patients except 67 who received warfarin for preexisting medical reasons or were in clinical trials of investigational agents. Adjuvant intermittent compression foot pumps were used while patients were in the hospital.

Results: There were a total of 8 deaths (0.28%); 4 from myocardial disease (0.14%); 2 from fatal PE (0.07%), 1 each from a cerebral vascular event and a fat embolus. There were 5 symptomic nonfatal PE requiring readmission (0.18%). Bleeding complications occurred in 10 patients (0.4%); 2 on a clinical trial for an investigational drug, 2 on warfarin and 6 on aspirin.

Discussion: The risk of fatal pulmonary embolus has been dramatically reduced in the past decade and this risk appears to be the same for most anticoagulant regimens at this time. The combination of widespread utilization of regional anesthesia, improved surgical techniques, early mobilization, short hospital stays, improved analgesic strategies, compression devices, and use of a chemoprophylactic agent, all combined, appear to have reduced this risk. Our results with aspirin demonstrate an incidence of fatal PE of 0.07% and an incidence of major bleeding of less than 0.4%. This experience compares well with other chemoprophylactic agents and offers a significantly reduced risk of bleeding and subsequent improved clinical outcomes. Carefully balancing the risks vs. benefits: aspirin continues to be our chemoprophylactic agent of choice.

11:36 a.m.

Rationale For and Results of Mechanical Thromboembolism

Prophylaxis For Total Hip Arthroplasty

Paul F. Lachiewicz, M.D.

Venous thromboembolism after total hip arthroplasty is related to activation of Virchow's triad intraoperatively with venous stasis, compression-kinking of the femoral vein and activation of the coagulation cascade. With activation of thrombogenesis "locally" in the operative limb, thromboembolism may be considered to be a specific local disorder in most patients. Thus, the author uses "localized" mechanical prophylaxis rather than systemic chemoprophylaxis. Mechanical prophylaxis decreases venous stasis by both an increase in venous velocity and venous volume. Pneumatic compression has also been shown to inhibit the coagulation cascade by a variety of methods. There are a wide variety of devices marketed for mechanical prophylaxis, including foot pumps, calf compression only devices and thigh-calf compression devices. Each device has its own proprietary mechanics, with different changes in peak venous velocity and venous volume.

The author has used one specific thigh-calf pneumatic compression device for mechanical prophylaxis begun intraoperatively in 1,032 consecutive primary and revision hip arthroplasties. Regional anesthesia was used in 95% of the procedures. Duplex ultrasonography was performed prior to discharge, and if negative, aspirin only was advised. Asymptomatic proximal thrombi were treated with anticoagulation. Using this protocol, the 30 day mortality was 0.3%. There was only one autopsy proven fatal pulmonary embolism (0.09%). The overall prevalence of thromboembolism was 4.6%, including symptomatic pulmonary embolism in 0.7%. The results of this study confirm the clinical efficacy of thigh-calf mechanical prophylaxis begun intraoperatively for almost all patients undergoing primary or revision total hip arthroplasty. There are rare exceptions which require chemoprophylaxis.

Mechanical prophylaxis using rapid inflation asymmetric calf compression in combination with aspirin or low molecular weight heparin has also been shown to significantly decrease the prevalence of thromboembolism compared to chemoprophylaxis alone. Foot pumps, which provide for the least increase in venous volume are probably less effective than circumferential thigh-calf or rapid inflation calf compression, with deep vein thrombosis reported in 6.6% to 13% of patients. Mechanical prophylaxis, with proven-effective devices, begun intraoperatively, should be routinely used in all total hip arthroplasty patients.

11:43 a.m.

Warfarin After THA for VTED

Vincent Pellegrini, M.D.

Complications of venous thromboembolic disease (VTED) remain the most common reason for readmission to the hospital following total hip arthroplasty. Declining lengths of hospital stay combined with a known risk of VTED related events extending to three months after operation present a dilemma in clinical management.

Longitudinal prospective analysis of contrast venography as a predictive screening tool was conducted over 20 years from 1984 through 2003 in 1,972 patients undergoing elective total hip arthroplasty in three university teaching hospitals. For the entire study period, patients with negative screening contrast venography received no further anticoagulation after hospital discharge, and those with documented deep vein thrombosis (DVT) were treated with warfarin (INR target 2.0) for 6 (calf thrombi) or 12 (thigh thrombi) weeks. Patients with pulmonary embolism (PE) were treated with warfarin for 6 months. From 1984 - 1992, patients who did not complete venographic screening were discharged without further anticoagulation. From 1993 - 2003, patients who did not complete venography were empirically continued on warfarin therapy for 6 weeks after discharge. All patients were audited at 6 months postoperatively, either by in-person followup visit or contact with the primary care physician. Readmissions for DVT, PE, or bleeding complications were recorded.

Contrast venography was completed in 1,032 patients and 175 (16.9%) were positive for deep vein thrombosis. The prevalence of venographic DVT was significantly reduced by a clinical pathway that included continuous epidural anesthesia by indwelling catheter maintained for 48 hours postoperatively (14.2% vs. 22.5%; p=0.0008). The overall readmission rate after THA for VTED was 1.62% (32/1972), including 14 PE (3 fatal) and 18 femoral DVT, compared with 0.6% after TKA. The subset of THA patients who were discharged on continued warfarin for any reason, including those with known DVT, had a readmission rate of 0.27% (1/360) for symptomatic VTED events compared with 2.2% (19/880; p=0.02, RR 0.128, OR 7.8) readmission among patients with negative venograms who were discharged home without further anticoagulation. Among all patients who were discharged without further anticoagulation, 31 of 1,612 patients (1.92%; p=0.02, RR 0.14, OR 6.9), including those without contrast venography in the first decade, were readmitted for clinically evident VTED events. Three patients (3/1,972; 0.15%) suffered fatal pulmonary embolism; all had negative venogram readings at time of hospital discharge and received no outpatient prophylaxis. There was one death (1/1,972; 0.05%) related to an intracranial bleed on warfarin therapy; autopsy demonstrated hemorrhage into an ateriovenous malformation.

Extended outpatient warfarin therapy after THA provides highly effective protection against readmission from VTED complications, including patients who formed thrombi while on primary warfarin prophylaxis. Moreover, there is no place for discontinuation of anticoagulation at time of hospital discharge, even in those patients whose screening contrast venography documented absence of deep venous thrombosis. Indeed, surveillance venography was a poor predictor of need for continued VTED prophylaxis and may be misleading when used to guide further anticoagulation therapy. We have discontinued routine DVT screening and recommend all patients receive extended VTED prophylaxis after hospital discharge following total hip arthroplasty.

1:15 p.m.

The John Charnley Award:

A Study of Implant Failure in Metal-on-Metal Surface Arthroplasties

Pat Campbell, Ph.D., Paul E. Beaulé, M.D., Edward Ebramzadeh, Ph.D., Michel LeDuff, M.A.,

Koen De Smet, M.D., Zhen Lu, Ph.D. and Harlan C. Amstutz, M.D.

The re-introduction of surface arthroplasty of the hip with hybrid fixation and metal-on-metal bearings has eliminated wear-induced osteolysis as the major cause of failure. To determine which modes of failure are now important, implant retrieval analysis was done on 98 failed metal-on-metal surface arthroplasty components from different manufacturers. Analysis involved sectioning the components, measuring cement mantle width and the depth of cement penetration, histopathology of the bone and measurement of the bearing wear. A finite element model was constructed to address the issue of thermal necrosis from bone cement. Femoral neck fracture and femoral1oosening were the main causes of failure. The finite element model showed that thermal necrosis of the bone could occur when cysts were filled with cement, and histological observations verified necrosis of interfacial bone, although adaptive remodeling was commonly seen. The amount of cement varied considerably with implant type and mode of failure. Cement penetration was greater in loosened components. These observations should be a cause for concern in light of the current cementing techniques where controlling the extent of penetration may be difficult. Optimizing cement mantle thickness to avoid leaving the component proud and avoiding cement over-pressurization to avoid extensive penetration into the femoral head may be important in reducing these modes of failure.

1:25 p.m.

The Frank Stinchfield Award:

Grafting of Biocompatible MPC Polymer on Cross-linked Polyethylene

Liner Surface for Extending Longevity of Artificial Hip Joints

Toru Moro, M.D., Yoshio Takatori, M.D., Kazuhiko Ishihara, Ph.D.,

Kozo Nakamura, M.D. and Hiroshi Kawaguchi, M.D.

Aseptic loosening induced by wear particles from the polyethylene (PE) liner is the most serious complication associated with total hip replacement. We prepared a novel hip PE liner with the surface graft of a novel biocompatible phospholipid polymer, 2-methacryloyloxyethyl phosphorylcholine (MPC), and reported that the grafting decreased the production of wear particles during a short term and the subsequent bone resorptive responses. For the clinical application, the present-study investigated the stability of the MPC grafting by the sterilization procedure and the wear resistance of the sterilized liner during longer loading comparable to clinical usage. Radiological spectroscopy analyses confirmed the stability of the MPC polymer on the liner surface after the gamma irradiation. A hip joint wear simulator trials up to 1.0 X 107 cycles using the sterilized cross-linked polyethylene liners with and without MPC grafting (CLPE and MPC-CLPE) revealed that the MPC grafting markedly decreased the friction, the production of wear particles, and the wear of the liner surface. This study demonstrated a marked improvement of wear resistance of the PE liner by the MPC grafting for clinically comparative periods even after the sterilization procedure, indicating that MPC grafting is a promising technology for extending longevity of artificial hip joints.

1:35 p.m.

The Otto Aufranc Award:

Clinical Significance of In Vivo Degradation for

Polyethylene in Total Hip Arthroplasty

Steven M. Kurtz, Ph.D., William Hozack, M.D., James Purtill, M.D., Michele Marcolongo, Ph.D.,

Matthew Kraay, M.D., Victor Goldberg, M.D., Peter Sharkey, M.D., Javad Parvizi, M.D.,

Clare M. Rimnac, Ph.D. and Avram A. Edidin, Ph.D.

Over the past six years, our research group developed a multi-institutional implant retrieval program to study in vivo degradation of polyethylene. The main focus of our collaboration has been to study the effect of in vivo exposure on mechanical properties, oxidation, and wear of polyethylene in the context of surgical and patient variables. We now have strong evidence to support our hypothesis that degradation of radiation-sterilized polyethylene occurs in the body for not only historical gamma air sterilized liners, but also for conventional gamma inert sterilized (ArCom) and annealed highly crosslinked polyethylene (Crossfire) liners as well. Our research has also led to the discovery that the most severe manifestations of in vivo oxidation typically occur in regions of the liner experiencing minimal wear, such as the rim of the component, where the body fluids (containing oxidizing species) has access to the polyethylene. Our data from historical, ArCom, and Crossfire retrievals all point to a. similar scenario in which the femoral head limits the in vivo oxidation of polyethylene at the bearing surface. Consequently, provided that rim impingement does not occur, and the polyethylene locking mechanisms remain relatively isolated from oxidizing fluid, in vivo oxidation does not appear to be clinically significant in the first ten years of implantation for conventional gamma sterilized polyethylene. Longer term, our research further demonstrates that in vivo degradation is associated with clinically relevant damage modes of rim damage and rim wear through in a specific acetabular component design (Hexloc) during the second decade of service. Based on our available data, we conclude that in vivo degradation must be included among the list of potential long-term failure modes for modular polyethylene components for THR.

1:45 p.m.

Summary Of Research Society Proceedings

Richard Coutts, M.D.

A synopsis of selected papers presented at this year's Orthopaedic Research Society related to this hip will be summarized.

2:00 p.m.

Medical Treatment After Femoral Neck Fracture: Does It Make A Difference?

Kenneth Koval, M.D.

The goal of hip fracture treatment is patient return to pre-fracture level of function. Surgical repair is the cornerstone of hip fracture management. However, data suggests that factors crucial for functional recovery are independent of fracture repair and are related to pre-fracture conditions and post fracture complications. Therefore, successful outcomes for hip fracture patients depends on an active partnership between Orthopaedic surgeon and others, including the medical consultant.

Patient care decisions are guided by well performed clinical studies. Conclusions are based on prospective randomized trials and not whether the procedure is fun, the author is a paid consultant or the rep buys lunch. Surgical delay slows patient mobilizabion and may affect functional recovery, however, failure to stabilize medical problems may increase risk for peri-operative complications. Level III evidence suggests that early surgical repair (24-48 hrs) in medically stable pts without active comorbid diseases is associated with reduction in 1 year mortality. However, pts who would benefit from surgical delay and further medical evaluation has not been well characterized.

Several aspects of treatment will be discussed including thromboprophylaxis, antibiotic prophylaxis, oxygen therapy, prevention of pressure sores, nutritional management and urinary tract management.

Delirium occurs in up to 60% of hip fx pats and is often unrecognized or misdiagnosed. It is shown to increase length of stay, risk of morbidity and mortality and institutionalization also may interfere with rehabilitation activities.

Interdisciplinary care will be outlined.

Successful outcomes for hip fracture patients depends on an active partnership between Orthopaedic surgeon and others, including the medical consultant.

2:07 p.m.

Total Hip Arthroplasty in the Treatment of Femoral Neck Fractures

William L. Healy, M.D.

Femoral neck fractures are common, and as the population in the United States increases and ages, the prevalence of femoral neck fractures is increasing. When femoral neck fractures occur, they cause considerable disability for the injured patient, and they consume considerable health care resources. Two distinct patient populations suffer hip fractures at the femoral neck: young patients with generally good bone stock and older patients with diminished bone stock. The extent of fracture displacement is a critical factor associated with outcome following femoral neck fracture. More fracture displacement is related to an increased rate of complications and less satisfactory results of treatment.

The goal of treatment of femoral neck fractures, regardless of patient age, bone stock, mechanism of injury, or displacement, is to restore pre-fracture function without morbidity due to the injury or the treatment. Optimal treatment for non-displaced fractures of the femoral neck is generally internal fixation with two to four parallel cancellous bone screws. Optimal treatment for displaced fractures of the femoral neck is controversial.

Surgical treatment options for displaced fractures of the femoral neck include: reduction and internal fixation; unipolar hemiarthroplasty; bipolar hemiarthroplasty; and total hip arthroplasty. Members of the American Association of Hip and Knee Surgeons were surveyed in 2004 to evaluate treatment preferences for displaced femoral neck fractures in the elderly. Ninety-eight percent preferred arthroplasty; two percent preferred reduction internal fixation. Specific arthroplasty treatment preferences were 87% hemiarthroplasty (48% unipolar; 52% bipolar) and 13% total hip arthroplasty. Reasons for not choosing total hip arthroplasty were patient ambulatory status, and risk of post-operative instability. ¹

At Lahey Clinic, we evaluated the efficacy of internal fixation, unipolar hemiarthroplasty, bipolar hemiarthroplasty, and total hip arthroplasty as treatments for displaced fractures of the femoral neck in elderly patients. One hundred and eighty-six consecutive non-randomized patients older or equal to 65 years of age with 186 displaced fractures of the femoral neck (Garden III and IV classification) were evaluated. One hundred twenty patients were treated with closed or open reduction and internal fixation. Forty-three patients were treated with hemiarthroplasty (unipolar or bipolar) and 23 patients were treated with total hip arthroplasty. One hundred twenty patients treated with internal fixation were compared with 66 patients treated with arthroplasty. Criteria for comparison were re-operations, mortality, hospital discharge disposition, functional outcome, living status, and cost effectiveness.
There was no difference in rates of re-operation between the groups. However, the mean interval to re-operation was significantly longer for the arthroplasty group than for the internal fixation group. There were no dislocations, infections, or re-operations for any patients treated with total hip arthroplasty.

Mortality was similar between the internal fixation and the arthroplasty treatment groups. However, the interval from operative treatment to death was significantly longer for patients treated with arthroplasty than with patients treated with internal fixation. Arthroplasty treatment was associated with a longer life after treatment of these fractures and none of the patients who died were treated with total hip arthroplasty.

There was no significant difference in the post-operative hospital disposition between the two groups.

Patients treated with internal fixation were less likely to maintain their home and independent status than patients who were treated with arthroplasty. Patients who were treated with internal fixation were also more likely to require nursing home care than patients who were treated with arthroplasty. Arthroplasty was associated with more independent living.

Arthroplasty was more cost effective than internal fixation.

Total hip arthroplasty was the best treatment for displaced fractures of the femoral neck in elderly patients based on pain relief, functional improvement, and cost effectiveness.²

1.        Iorio R, Macaulay WB, Healy WL, Teeny SM. Surgical treatment of displaced femoral neck fractures. J. of Arthroplasty 20:267. 2005 (presented @ AAHKS, Dallas TX, November 2004).

2.        Healy WL, Iorio R. Total hip arthroplasty: Optimal treatment for displaced femoral neck fractures in elderly patients. Clinical Orthopedics and Related Research, December 2004.

2:14 p.m.

Femoral Neck Fractures: Bipolar versus Unipolar

M.E. Cabanela, M.D.

For patients under 60 years of age with a displaced femoral neck fracture, the most common recommended treatment is reduction, open or closed, and internal fixation with screws, particularly if the bone quality is satisfactory. However, for patients over 60, arthroplasty enters the surgical armamentarium specifically if the patient's bone quality is poor. Total joint replacement arthroplasty, while very popular for this diagnosis in Europe and Asia, has not reached the same popularity in the United States and it is associated with a high incidence of dislocation. This high dislocation rate can be reduced with proper attention to technical detail, but the vast majority of femoral neck fractures treated by arthroplasty in this country are treated not by joint replacement surgeons but by general orthopedic surgeons and often by junior orthopedists. It is therefore not surprising that the majority of these patients are treated by hemiarthroplasty, a quick, common and reliable procedure.

The choices of fixation for hemiarthroplasty are cementless or cemented and the hemiarthroplasty types can be unipolar or bipolar.

The choice of fixation appears to have been solved in the literature. The use of cement is associated in prospective randomized studies with better function and less pain. Cement, however, has the risk of acetabular protrusion (what the French have called cotiloiditis= acetabular erosion) ; in addittion cement has been associated with sudden death during arthroplasty. In a study of almost 40,000 arthroplasties, Parvizi found incidence of intraoperative death of 0.18% for arthroplasties done for fractures whereas that incidence was 6 times less in arthroplasties done for other reasons. This has to do with the bone cement implantation syndrome, a condition of hypotension, hypoxemia, arrhythmias and cardiac arrest that is caused by venous embolization from intramedullary hypertension and occurs at the time of cemented arthroplasty. This condition can be significantly decreased by the use of pressure lavage prior to implantation of the cement.

It appears, however that cement provides better results on hemiarthroplasty than cementless prostheses in the majority of the patients. Perhaps in the very old patient with significant comorbidities, particularly cardiac co-morbidities, specifically if that patient is not very mobile (ie. a nursing home resident), an uncemented prosthesis might do just as well.

The issue that is not as well clarified in the literature is the use of a bipolar versus a unipolar prosthesis. Bipolars are associated with perhaps a better range of motion, less dislocation rate and a longer survivorship than unipolars and when the patients are community ambulators, they appear to have done better: however, this advantage of the bipolar over the unipolar is not supported universally and in fact, in the literature one can find support for any attitude one might choose.

The current attitude with displaced femoral neck fractures at our institution is to treat them by hemiarthroplasty if the patient is over 60 or 65 years old, the bone quality is poor, and the fracture is displaced. If the patient is a community ambulator a bipolar arthroplasty is the preferred choice. If the patient is a nursing home resident with minimal level of activity, especially if there are associated comorbidities, then a unipolar Austin Moore uncemented prosthesis is the procedure of choice. We limit the use of total hip replacement to patients with preexisting hip disease or certain special individuals with a high level of function who for some reason are not candidates for reduction and fixation with screws.

2:21 p.m.

The Management of Femoral Neck Fractures in Children

John M. Flynn, M.D.

Historically, femoral neck fractures in children have been associated with a very high rate of serious complications. In historical series, avascular necrosis has ranged up to 47% and coxa vara up to 32%. Over the past two decades, there has been an increased attention on the management of pediatric femoral neck fractures to decrease these complications. Pediatric femoral neck fractures are usually classified by using Delbet's classification. Type I fractures are physeal fractures, Type II are midfemoral neck fractures, Type III are basi cervical fractures and Type IV are inter-troch fractures. It is well known that the rate of avascular necrosis decreases as the fracture type progresses from I to IV. We reviewed 18 patients from our level 1 trauma center who had a displaced non-pathologic fracture of the hip sustained before the age of 16 years old. This series represented a 20-year cumulative experience at our center for these relatively uncommon injuries. The mean age at time of injury was 8 years (range, 2 to 13 years old). The patients returned for re-evaluation and radiographs with a mean follow-up of 8 years (range, 2 to 17 years). Each patient at our center was treated by early closed or open reduction (within 24 hours of injury) with internal fixation. Sixteen of the children had immobilization in a spica cast. In our series, we had 1 Type I, 8 Type II, 8 Type III, and 1 Type IV. All fractures in our series were displaced. We had no complications in 15 patients. We had avascular necrosis in one patient with a Type III fracture and one non-union in a Type II fracture. Two of our patients were not immobilized in a spica cast, and one of them sustained the non-union.

Since the publication of our study in 2002, there have been other series with modern internal fixation and more urgent treatment. The complication rate has markedly decrease compared to historical series. Our current practice is to treat a displaced femoral neck fracture in a child as a surgical emergency, equivalent to compartment syndrome, and certainly more urgent than an open fracture. We routinely do a decompression or aspiration of the inter-capsular hematoma, reduce the fracture, and use stable internal fixation. If the fixation does not extend into the femoral epiphysis, then a spica cast is used. This is most common in fracture of the mid femoral neck or basi-cervical fractures in children younger than 10 years of age. In these cases, the surgeon does not want to cross the physis with fixation. We and others have experienced a loss of fixation when we try to mobilize children rapidly without placing fixation into the femoral epiphysis.

In summary, the modern management of pediatric femoral neck fractures includes urgent reduction and decompression of the capsule, stable internal fixation, and a short period of spica cast immobilization for those children whose fracture pattern or age prevents the surgeon from placing the internal fixation all the way into the femoral epiphysis.

3:03 p.m.

Fully Coated Stems - Is This the Gold Standard?

Daniel J. Berry, M.D.

Advances in implants and operative method have markedly improved the results of femoral revision. Conventional uncemented stems and monoblock proximally porous-coated stems had mostly poor results, hence most recent efforts have focused on one of three techniques: impaction bone grafting with cement, fluted tapered modular stems, and extensively porous-coated stems.

The bulk of the literature reports high rates of implant fixation with extensively porous-coated stems. Furthermore, extensively coated stems are compatible with a wide range of bone deficiencies and also with extended greater trochanteric osteotomy. Drawbacks of extensively coated stems include risk of proximal stress shielding, fracture risk during insertion, and difficulty of extraction once bone ingrown.

The author will present ten-year survivorship data on extensively porous-coated stems from one large center focusing on implant survivorship, determinants of success and failure, and limitations of the method.

3:10p.m.

Femoral Revision Arthroplasty with Fluted Modular Titanium Stems

Donald Garbuz, M.D., MHSc, FRCSC

Cylindrical, non-modular, extensively coated, cobalt chromium stems are arguably the gold standard in uncemented total hip revision arthroplasty in North America. While popular in Europe for many years, tapered, fluted, modular, titanium stems have been more recently introduced in North American as an alternative concept in stem design and are increasing in popularity. The features of this stem design have the potential to improve patient outcomes. Modularity facilitates intraoperative adjustment of leg length, horizontal offset and neck version. Theoretically, the reduced stiffness should reduce proximal stress shielding as well as thigh pain. However, these theoretical advantages have not yet been demonstrated by way of superior clinical outcomes. The purpose of this study was to compare quality of life after the use of 2 different femoral designs; a modular tapered and fluted titanium design compared with a cylindrical and extensively porocoated stem made of chrome-cobalt with single modularity (head size and neck length alone) in revision total hip arthroplasty.

This cross sectional outcome study analyzed the subjective quality of life, following revision total hip arthroplasty, in two hundred and twenty patients, with a minimum follow up of two years. From our database a cohort of patients who had undergone revision hip replacement between August 1998 and December 2003 with a tapered, fluted, modular, titanium stem (ZMR stem, Zimmer, Warsaw, USA) was identified. A control group of patients who had undergone revision with a cylindrical, cobalt chromium alloy revision stem (the Solution stem, Depuy, Warsaw, USA) was also identified. This group was matched for age by decade and gender. Patients were excluded from both groups if their revision had been undertaken for infection, recurrent dislocation or if their acetabular reconstruction had required a reconstruction cage, structural allograft or a constrained liner. Subjective outcome assessment and patient satisfaction were measured using the WOMAC Osteoarthritis Index, the Oxford Hip Score, the SF-12 and the Arthroplasty Satisfaction Scale. Two matched, comparative cohorts were established based on the type of stem use.

At final follow up, all of the quality of life measures favored the tapered, titanium stem. The WOMAC pain, function and overall scores were all higher in this group as well, achieving greater than 9 percentage points difference in the pain domain (p=0.03, 0.02 and 0.02 respectively). The Oxford Hip Score and the Satisfaction score reflected an even greater difference in outcome between the two stem designs p=0.006 and p<0.0001 respectively.

We hypothesis that the reduced stiffness of the titanium stem, coupled with the interface rotational stability and intraoperative modularity likely resulted in the improved patient outcomes observed in this study.

3:17p.m.

Cages - The Current Role

Wayne Paprosky, M.D., Michael R. O'Rourke, M.D. and Scott M. Sporer, M.D.

Introduction: The purpose of this study was to evaluate the results of cage reconstruction for severe acetabular defects. Our hypothesis was that the mechanical failure rates increase in the midterm follow-up due to graft remodeling and fatigue failure of the components.

Methods: Forty-five revision acetabular cage reconstructions (41 patients) were followed-up at an average 5 years (range 2-8 years). The acetabular classification according to the senior author was 4 type 2C, 21 type 3A, and 20 type IIIB. Outcomes included Merle D'Aubigne scores, revision, radiographic loosening, and complications. Three patients died before a minimum 2-year follow-up without revision. Structural allograft was used in 11 cases (including 3 total acetabular transplants) and cancellous allograft was used in 26 cases. Constrained liners were used in 16 cases.

Results: Nine (20%) were revised or resected due to aseptic loosening (7/9) and sepsis (2/9) at an average 49 months. An additional eleven hips (24%) are definitely or probably loose and three (7%) are on chronic antibiotics for infection. Merle D'Aubigne for pain and walking increased from 4.4 to 7.8 at the final follow-up. Complications included 6 infections, 5 nerve palsies, and 3 dislocations.

Discussion: Acetabular revision with the presence of significant bone loss is challenging. Acetabular cages enhance the mechanical stability of a cemented cup and protect underlying allograft when bone loss precludes the use of an ingrowth prosthesis. The failure rate of cage reconstructions for these difficult cases is concerning at intermediate follow-up and emphasizes the need for alternative solutions.

3:24 p.m.

Trabecular Metal in Acetabular Reconstruction

David G. Lewallen, M.D., Arlen D. Hanssen, M.D.,

William J. Long, M.D. and Nicholis O. Noiseux, M.D.

In the mid- 1990's a novel biomaterial became available for orthopedic applications consisting of a interconnected scaffold of highly porous pure tantalum with an ultrastructural appearance resembling trabecular cancellous bone. Properties of this material include a high coefficient of friction for exposed surfaces, overall porosity exceeding 80%, and reduced structural stiffness compared to conventional implant materials and coatings. Dramatic experimental animal studies documenting extensive bone ingrowth suggested the possibility of improved strength and durability of implant fixation in instances of limited bone contact or impaired bone quality. Beginning in 1997 with a monoblock acetabular component, and subsequently in 1999 with a two-piece revision shell fixed by multiple screws, this material has had particular appeal for use in difficult acetabular reconstruction and revision surgery. Porous tantalum trabecular metal augments designed to fill major bone defects have also been fabricated as prosthetic alternatives to structural bone graft when critical implant fixation is lacking. This review will summarize the experience to date in 1212 acetabular reconstructions performed between July 1997 and Jan 2004 (613 primary, and 599 revisions) with special focus on the technique and patterns of usage of adjunctive acetabular augments and modular cage extensions which have been designed to extend the use of this material in cases of massive bone loss and pelvic dissociation. Follow-up at 2 to 8 years post surgery has revealed an overall reoperation rate for any cause of 69 out of 1212 , with 21 of 613 primary cases and 48 of 599 revision cases requiring a reoperation. Of the 48 revision cases reoperated, 16 involved removal of the trabecular metal acetabular shell for reasons of deep sepsis (12), malposition and hip instability (2), and aseptic loosening (2). Loosening of the porous tantalum trabecular metal shell was associated with persistent nonunion of a pelvic dissociation in one, and avascular necrosis of periacetabular bone in the other. Deep infection represented the greatest risk to cup survivorship in this series.

These results suggest that durable acetabular fixation can be achieved even in the face of major bone loss using a modular porous tantalum trabecular metal revision shell system which facilitates initial stable mechanical purchase against host bone.

3:31 p.m.

Impaction Grafting Of The Socket

John Timperley, Ph.D.

Acetabular component loosening and pelvic osteolysis continue to be a significant clinical challenge in revision hip arthroplasty. Impaction grafting with implantation of a cemented socket is a technique widely employed as a surgical option in both cavitary and segmental defects. We present results of 339 cases of acetabular reconstruction with impacted allograft.

All patients who underwent acetabular reconstruction with impaction allograft between July 1995 and July 1999 were included. Clinical and radiographic data was collected prospectively.

There were 339 patients. The average age was 71 years. Most were first time revisions (201) but the group included 2nd, 3rd and 4th revisions with 34 two-stage revisions and 44 primary arthroplasties. There were multiple surgeons carrying out the operations with 2/3 being consultants and 1/3 fellows.

Pre and post-operative clinical assessment included Oxford and Harris hip scores, and a Charnley modified d'Aubigne-Postel score for pain, function and range of movement.

Pre-operative radiographs were classified using the Paprosky classification. Follow up radiographs were assessed for graft thickness, component migration, graft resorption and radiolucent lines.

There were 10 grade I, 205 grade II, and 103 grade III defects with 3 pelvic discontinuities. Reconstruction methods included impaction only, rim and/or medial mesh, Kerboul Postel plate fixation and reinforcement cages.

The average follow up was 8.1 years (6.3 - 10.4) and no patient was lost to review. Infection was identified in 15 patients (7 recurrent and 8 new - 2.6%). There were 6 nerve injuries; 2 remain unresolved. 15 patients dislocated (4.4%). There have been 88 deaths in the group with 3 being in the peri-operative period.

There have been 15 re-operations for aseptic loosening. Nine large rim meshes failed. One medial wall mesh and one acetabulum reconstructed with impaction only also loosened. Three Kerboul Postel plates fractured and 1 cage migrated.
The survivorship with any re-operation as the end-point was 86% at 10-11 years. With aseptic socket loosening as the end-point the survivorship was 93% over the same period.

Factors associated with aseptic loosening include use of a large rim mesh particularly with an allograft thickness of >2cm. In addition, use of bone other than untreated fresh frozen material carried an increased risk for revision.

Conclusion
We conclude that impaction allografting is a reliable method for acetabular reconstruction. Careful consideration should be given when allograft thickness will be >2cm or a large rim mesh is required. Fresh frozen allograft material preformed better than graft that had been pasteurised or irradiated.

6

3:53 p.m.

Patient Selection Variables for Minimally Invasive Surgery

Thomas P. Sculco, M.D.

Minimally (less) invasive total hip replacement requires proper patient selection to lessen rate of complication and promote a successful arthroplasty. Since surgical windows are more limited to insure proper visualization patients who have Body Mass Index of less than 30 are ideal. This applies to both single and two incision procedures although those utilizing two incision techniques have stated body mass is not an issue in the approach. Certainly as body weight and obesity increase more extensive exposures will be necessary. Through single incision less invasive procedures graduated increase in exposure may be performed and this is not the case with two incision approaches. As a rule less invasive surgery is not recommended in patients with BMI >35. Additionally patients with complex primary hip pathology are best performed through more extensive approaches. These include patients with high riding hip dislocation (Crowe 4), severe hip ankylosis with or without protrusion and patients with severe soft tissue scarring secondary to extensive prior hip surgery. An additional group that may pose a problem with visualization and soft tissue retraction is the heavy, well muscled, short stature usually male patient. In these patients, especially if the hip joint is stiff, exposure is difficult and exposures should be extended. Patients undergoing revision hip surgery also are not ideal candidates for these less invasive approaches as failed implant removal, bone grafting and augmentation usually require additional visualization.

4:00 p.m.

Direct Anterior Approach

William Hozack, M.D.

My approach to THA is to make one incision as small as possible but as large as necessary, to obtain direct visualization of the bony anatomy and to use modified instrumentation in order to minimize soft tissue trauma. I use the direct anterior (modified Smith Peterson) approach selectively in my practice. The direct anterior (DA) approach goes between muscle intervals and, more importantly, between nerve innervations - the tensor fascia femoris and gluteus medius muscles are innervated by the superior gluteal nerve (CHECK) and the sartorius and rectus femoris muscles are innervated by a branch of the femoral nerve. The lateral femoral cutaneous nerve is at risk in the traditional DA approaches, but a more lateral incision virtually eliminates this problem. During a learning curve of 50 operations I learned several things. First, not every patient is ideal for this approach. Obese patients (BMI > 30) can be done through the DA approach, but the minimally invasive character of the operation is compromised. Patients with poor bone quality and significant abnormalities of the bony anatomy make the operation through a DA approach more difficult and the results less satisfying. Proper instrumentation is very important in minimizing the soft tissue damage and a prosthesis designed specifically for the approach facilitates the procedure.

A cadaver study was performed to evaluate muscle damage with the DA approach as compared to a mini-posterior approach. In six cadavers operated with both approaches, the DA approach resulted in significantly less damage to the abductor mechanism. The price was more damage in the anterior muscles - TFL, rectus femoris. It is quite clear that all MIS approaches damage soft tissue to some extent.

A recent prospective study is ongoing evaluating the DA and direct lateral approaches. In this study the pain management protocols, anesthesia, patient selection criteria, surgeon, and physical therapy regimens were identical between the groups. The early preliminary results do suggest faster recovery and reduced pain in the DA group.

4:07 p.m.

The 2-Incision THA: Its Role in 2006

Mark W. Pagnano, M.D.

Two-incision minimally invasive total hip arthroplasty captured the interest of patients and surgeons alike when it was widely touted in the lay press beginning in 2002. A lack of peer-reviewed scientific data made it difficult for the interested orthopedic surgeon to determine if it was patient selection, patient expectation, rapid rehabilitation programs, comprehensive pain management protocols or the 2-incision technique itself that accounted for the reported early functional benefits. Early reports from developers of the 2-incision technique suggested rapid rehabilitation with a low prevalence of complications. Most surgeons remember a report in which 100 2-incision THAs were done with 100% going home in less than 1 day; 100% free of dislocation; 100% free of reoperation; 100% free of readmission; 100% free of complication at home. Combined data on 375 patients from 4 surgeon developers showed 1.3% major complications and 2.1% minor complications in patients with a mean age of 56, weight of 185 lbs and 2/3 of whom were male.

Subsequent data from non-developer surgeons has been less encouraging. Archibeck and White tracked the early experience of 159 surgeons and found that key complications did not decrease over the first 10 cases and that many surgeons abandoned the technique before reaching case #10. Mardones et al. cadaver study showed that the 2-incision technique could not be done without routinely damaging the abductors, the external rotators or both and that the extent of muscle damage was significantly greater with a 2-incision than with a mini-posterior THA technique. Pagnano et al. showed that 80 consecutive unselected 2-incision patients had modest early functional outcomes and substantial complications in 14% of cases. Bal et al. reported a 10% reoperation rate and 25% incidence of lateral femoral cutaneous palsy in 89 consecutive 2-incision THA.

Emerging data that directly compares 2-incision THA to other techniques is now available. Pagnano et al. reported on 26 patients who had a 2-incision THA on one side and a mini-posterior THA on the contralateral side using the same anesthetic, pain management and rapid rehabilitation protocol. Two-thirds of the patients preferred the mini-posterior THA, most often because they perceived a quicker recovery after the mini posterior side. Two subsequent studies from those authors include a Prospective Randomized Trial of 2-Incision versus Mini-posterior THA and a Comprehensive Gait Analysis Study of 2-incision versus mini Posterior THA. Both studies show no substantial early functional benefit of the 2-incision technique.

In conclusion, in 2006 there is no scientific data that a 2-incision THA is functionally superior to other THA approaches. Basic science cadaver studies dispel the notion that 2-incision THA can be done without cutting or damaging muscle or tendon. For many surgeons the prevalence of complications is high when adopting the 2-incision technique. Patients who have had a 2-incision THA and mini-posterior THA more often prefer the mini-posterior. Finally, the added technical difficulty of the MIS 2-incision THA has not been rewarded with a better functional outcome or a better cosmetic result when applied to similar groups of patients.

4:14 p.m.

Management of Perioperative Pain

Lawrence D. Dorr, M.D.

Pain management for total hip replacement has had significant changes in the past five years. The purpose of this study was to document the outcome of patients treated with a multimodal pain program designed to avoid parenteral narcotics. Fifteen percent of 140 patients needed parenteral narcotics postoperatively with only nine patients (6.4%) using parenteral narcotics after the day of surgery. Pain scores were below three of ten on all postoperative days. Emesis occurred in five patients (3.6%). One hundred and thirty-eight patients (98.6%) were discharged home. Fifty-eight percent of patients had sufficient balance and strength to be discharged home on a single point cane. This multimodal pain management program was effective in providing pain relief, nearly eliminating emesis, and accelerating function.

4:21 p.m.

Comprehensive Approach to Rehabilitation

Benjamin E. Bierbaum, M.D.

The need for rehabilitation following total joint arthroplasty has been identified as a topic of debate in the orthopedic community, especially in recent history with the introduction of minimal surgery. Proponents of rehabilitation acknowledge that individual surgical skill and a comprehensive peri-operative program directed to the patient's needs and interests ensures not only a successful hospital stay, but also lifelong success.

A comprehensive rehabilitation program begins by addressing a patient's pre-operative needs, as research indicates that patient expectations have shown to be important predictors of improved functional outcomes and satisfaction following total joint arthroplasty.¹ Pre-operative preparation should include: patient education, therapeutic exercise (cardiac activity and upper extremity conditioning), pre-admission planning, discharge planning, equipment check and home evaluation. A personal phone call to the patient, from the surgeon, the day before surgery helps to decrease pre-surgical anxiety and reinforces the surgical/hospitalization/rehabilitation plan.

Physical and occupational therapists are not exclusive members of the hospital rehabilitation team. Active involvement of all orthopedic caregivers, medical consultants, anesthesia, pain management, nursing, nutrition, and case management is essential. Physical therapy may be initiated on the day of surgery with focus on bed mobility, supine exercises, sit to stand transfers and gait with assistive devices as appropriate. Advance knowledge of the surgeon's rehabilitation protocols facilitates an uncomplicated hospital stay and discharge process.

Specific patient guidelines should be outlined for the first four weeks following discharge to home. These guidelines may include ROM limitations, home exercise programs, proper use of assistive devices and functional mobility instruction. DVT prophylaxis should be stressed. After four weeks, the emphasis of the rehabilitation program should shift toward the patient's ever changing post-operative interests and needs. Primary TJA is a "quality of life" surgery. A comprehensive rehabilitation program should encompass areas that lead to improved quality of life for our patients.

1.        Mahomed N, Liang M, Cook E, et al. The Importance of Patient Expectations in Predicting Functional Outcomes After Total Joint Arthroplasty. J Rheumatol 2002;29:1273-9.

4:28 p.m.

Measurable And Clinically Relevant Outcomes

Aaron G Rosenberg M.D.

Health care policy research has undergone paradigm shift in the method recommended for evaluating the results of treatment. A radical switch in orientation from health status representing the "absence of disease" to a "state of physical, mental, and social well being" has led to the development and incorporation of general health outcomes measures in the evaluation of patients. These instruments are demonstrably more accurate in representing the health status of the patient both before and after intervention, as well as being applicable to broad cohorts of patients across a broad range of health care conditions and interventions.

Outcomes instruments (whether general health related or disease or intervention specific) must be supported by appropriate psychometric testing, and meet 3 basic requirements to be considered appropriate for measuring purported outcomes. They must be validated by appropriate testing to insure that the instrument measures what it purports to measure: that is the instruments findings must be compared to an established or well documented health status. The instrument must also be reliable: providing a low noise to signal ratio when evaluating the subject at different times when no clinical changes have occurred. Conversely, it must also be responsive: able to measure small or subtle changes which occur over time. The same measures of validity must be present for disease or intervention specific outcomes tools.

New and innovative procedures (and implants) are not always accompanied by the type of data with which clinicians can make good decisions about applicability. Early studies are commonly related to procedural feasibility, and are associated with the recognition of those hurdles and pitfalls, which must be overcome to demonstrate a clinical viability threshold. Multiple additional confounding issues in the selection of patients may limit their applicability regarding the general adoption of new procedures

In order to follow one of the basic tenets of the medical profession, to "do no harm", studies by multiple investigators should be available for practitioners to assess the potential risks and complications which may be encountered in the utilization of the new procedure. Standard reporting methodologies of complications rates should suffice for these purposes. However, in order to maintain applicability over a broad patient population, such studies must include adequate demographic information to allow the clinician to understand the population reported. In particular, age, gender and co-morbidities, all of which have been shown to bias outcomes must be accounted for in descriptive or comparative studies.

Collecting and assessing general health, disease or intervention specific outcomes measures, in cases where the effects of the intervention are large, unfortunately creates a paradoxical situation for data interpretation. The presence of a large standardized effect size (as is seen in joint replacement) creates such a loud "signal", that the more subtle signals of interest under evaluation can be obscured. This problem would seem to be magnified by evaluation of the potentially more subtle signs of early recovery, as would be expected by the claims of MIS proponents. Therefore, any treatment effect is not likely to be clearly evaluated by the more gross measurements of health that have been used to study arthroplasty traditionally. While the evaluation of less invasive surgical techniques should eventually incorporate traditional general health assessment and disease or intervention specific instruments, measurement of the smaller interval changes claimed for early recovery, will require alternate methods and time frames for data collection.

Finally, utilization of appropriate study design will be needed to more thoroughly evaluate the specific advantages of these interventions. Recognition of the compounding effects of patient selection, varying peri-operative management techniques and other factors along with the use of appropriately structured information retrieval techniques will be needed to prevent the introduction of significant bias. While difficult to carry out, looking at specific variables of interest with randomized, prospective trials (as blinded as can be accomplished in this setting) will eventually be required to assess the actual benefits of these techniques.

OFFICERS OF THE HIP SOCIETY

President:

James D'Antonio, M.D.

First Vice-President:

John Callaghan, M.D.

Second Vice-President:

Lawrence Dorr, M.D.

Secretary-Treasurer:

William Maloney, M. D.

Member At Large:

Paul Lachiewicz, M.D.

Chairman Ed Committee:

William Maloney, M. D.

Immediate Past President:

Richard White, M. D.

OFFICERS OF THE AAHKS

President:

Joseph C. McCarthy, Jr., M.D.

1st Vice President:

William J. Hozack, M.D.

2^nd Vice President:

Daniel Berry, M.D.

3^rd Vice President:

David G. Lewallen, M.D.

Secretary:

James B. Stiehl, M.D.

Treasurer: 

Carlos J. Lavernia, M.D.

Immediate Past President:

Richard F. Santore, M.D.

Members at Large:

Brian Parsley, M.D.

Thomas Fehring, M.D.

Richard E. White, M.D.

Brian J. McGrory, M.D.

Educational Committee Chair:

Arlen D. Hanssen, M.D.